A novel class of amphiphiles with sulfate groups at the C-6 position and palmitoyl groups at the C-2, 3 positions of α-, β-, and γ-cyclodextrin (CD) were efficiently synthesized. These compounds formed stable monolayers with high collapse pressures at the air-water interface. The mixed monolayer behaviors of the 6-O-sulfated CD amphiphiles (SO3-CDC16) in the presence of dipalmitoyl phosphatidylcholine (DPPC) and cholesterol were discussed using the surface pressure-molecular area (π-A)

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... . The collapse pressures showed maxima at molar ratios of SO3-CDC16 lower than 10 mol%. A morphological analysis of the liposomes containing DPPC and 4 mol% SO3-CDC16 formed in PBS was carried out using transmission electron microscopy with negative staining, and vesicles with maximum diameters of 350 -500 nm were observed. Moreover, the releasing ability of these liposomes was examined using a fluorescent compound, calcein. It was clearly shown that liposomes containing SO3-CDC16 could release encapsulated calcein more easily than liposomes consisting only of DPPC, and that the release rate depended on the phase transition temperature of the SO3-CDC16 included in the liposome membrane.